The long term goal of this research is to determine the role of anaerobic bacterial infection as a cause of chronic, intermittent, low grade intraocular inflammation following intraocular lens (IOL) implantation and cataract extraction. Experience with prosthetic devices implanted elsewhere in the body suggests that low-grade inflammation may be due to anaerobic bacterial infection at the site of the prosthesis. The role of an intraocular lens in predisposing the aphakic eye to chronic Propionibacterium acnes endophthalmitis will be studied in aphakic and pseudophakic rabbit eyes. A standardized cataract extraction technique (phacoemulsification), with and without posterior IOL implantation, has been developed in the rabbit eye. The dose-response curve of endophthalmitis following the anterior chamber injection of P. acnes (the common anaerobe on the lid margin) will be established in aphakic and pseudophakic rabbit eyes using clinical and microbiologic studies. Based on the dose-response curve, we will establish a reproducible model of chronic post-operative aphakic and pseudophakic P. acnes endophthalmitis and compare and contrast the long and short term natural course of these entities (including clinical, histopathologic, and microbiologic features). We will evaluate appropriate clinical and laboratory methods to better recognize and treat the chronic inflammation associated with low-grade anaerobic endophthalmitis. This work represents a collaboration between an established anaerobic bacterial laboratory and an ophthalmologic research center (Smith, USC).